PHOSPHATE FERTILIZERS 173 



to 15 per cent, of phosphoric acid, 10 to 12 per cent, 

 of nitrogen, and from 5 to 7 per cent, of alkaline salts. 



BONE FERTILIZERS 



221. Raw Bones contain, in addition to phosphate 

 of lime, Ca (PO ) 2 , organic matter which makes them 

 slow in decomposing and slow in their action as a fer- 

 tilizer. Before being used as a fertilizer they should be 

 fermented in a compost heap with wood ashes in the 

 following way, a protected place being selected so that 

 no losses from drainage will occur. A layer of well- 

 compacted manure is covered with wood ashes, the 

 bones are then added and well covered with manure 

 and wood ashes. From three to six months should 

 be allowed for the bones to ferment. The large, coarse 

 pieces may then be crushed and are ready for use. 

 The presence of fatty material in a fertilizer retards its 

 action because fat is so slow in decomposing. Bones 

 from which the organic matter has been removed are 

 more active as a fertilizer than raw bones. Bones 

 contain from 18 to 25 per cent, of phosphoric acid and 

 from 2 to 4 per cent, of nitrogen. The amount and 

 value of the citrate-soluble phosphoric acid are extre- 

 mely variable. 



222. Bone Ash is the product obtained when bones 

 are burned. It is not extensively used as a fertilizer 

 because of the greater commercial value of bone-black. 

 It contains about 36 per cent, of phosphoric acid, and 

 is more concentrated than raw bones. 



223. Steamed Bone. Raw bones are subjected to 

 superheated steam to remove the fat and ossein to be 



